1. Field of Invention
The invention relates to a projector and, in particular, to a self dust-off apparatus for the projector.
2. Related Art
The cooling structure of a conventional projector 10, as shown in FIG. 1A, has the inlet 11 and the outlet 12 formed on the projector housing 13. A fan 14 is provided between the inlet 11 and the outlet 12 for driving cooling air from the inlet 11 into the housing 13 to cool down the power supply 15. Afterwards, the cooling air is guided to cool down the bulb 16 and finally expelled outside the housing 13 via the outlet 12.
As shown in FIG. 1B, the airflow on the inlet side 141 of the fan 14 is a laminar flow, while that on the outlet side 142 is a turbulent flow with swirls. Since the laminar flow has thicker boundary layers, dust in the air is likely to gradually deposit on the fan 14 and other elements on the inlet side 141 (e.g. the power supply 15). With the accumulation of dust, the efficiency of the fan is lowered and the thermal resistance of the power supply 15 is increased. Therefore, the projector has to be cleaned periodically in order to remove dust on the fan 14 and the power supply 15. Generally speaking, it becomes more difficult to remove dust as the volume of the projector and its internal space get smaller. Besides, one may install a filter (not shown in the drawing) at the inlet 11 to filter the cooling air entering the projector 10. However, this reduces the amount of airflow into the projector. One then has to increase the fan speed to obtain the desired airflow. Nevertheless, this method has the problem of noises.
Therefore, how to effectively remove dust in the projector is an important issue in the field.